A381154 Decimal expansion of the isoperimetric quotient of a regular 9-gon.

9, 5, 9, 0, 5, 0, 5, 4, 1, 8, 7, 3, 6, 0, 9, 3, 5, 8, 0, 7, 4, 5, 4, 3, 3, 0, 6, 7, 0, 8, 6, 4, 3, 4, 1, 3, 0, 2, 0, 1, 8, 1, 5, 8, 0, 9, 7, 5, 2, 8, 5, 8, 7, 3, 4, 3, 7, 2, 0, 7, 8, 9, 2, 8, 0, 3, 9, 1, 9, 4, 5, 1, 0, 3, 7, 5, 6, 4, 9, 7, 6, 1, 4, 4, 0, 5, 7, 7, 1, 2

Offset

0,1

Comments

For the definition of isoperimetric quotient, see A381152.

Links

Paolo Xausa, Table of n, a(n) for n = 0..10000

Eric Weisstein's World of Mathematics, Isoperimetric Quotient.

Wikipedia, Isoperimetric inequality.

Formula

Equals Pi/(9*tan(Pi/9)) = Pi/(9*A019918).

Equals (4/81)*Pi*A256853.

Example

0.959050541873609358074543306708643413020181580975...

Mathematica

First[RealDigits[Pi/(9*Tan[Pi/9]), 10, 100]]

Crossrefs

Cf. A019918, A256853.

Cf. isoperimetric quotient of other regular polygons: A073010 (triangle), A003881 (square), A381152 (pentagon), A093766 (hexagon), A381153 (heptagon), A196522 (octagon), A381155 (10-gon), A381156 (11-gon), A381157 (12-gon).

Sequence in context: A090463 A272795 A246765 * A191759 A289505 A371528

Adjacent sequences: A381151 A381152 A381153 * A381155 A381156 A381157

Keyword

nonn,cons,easy

Author

Paolo Xausa, Feb 15 2025

Status

approved